Lifting clamp



P. V. OQUINN LIFTING CLAMP Dec. 3, 1968 4 Sheets-Sheet 1 FIG. 2.

Filed Oct. 19, 1966 INVENTOR PAUL v. oouuwv BY J Zm/M P V. O'QUINN LIFTING CLAMP Dec. 3, 1968 4 Sheets-Sheet 2 Filed Oct. 19, 1966 FIG. 4.

FIG. 3.

PAUL v. o'ow/wv INVENTOR Dec. 3, 1968 v, O'QUINN 3,414,315

LIFTING CLAMP Filed Oct. 19, 1966 4 Sheets-Sheet 5 g FIG. 6

INVENTOR MM; p c /w g g P. V. O'QUINN Dec. 3, 1968 LIFTING CLAMP 4 Sheets-Sheet 4 Filed Oct. 19, 1966 PAUL 1/. O'OU/NN.

INVENTOR ATTORNEYS United States Patent 3,414,315 LIFTIN-G CLAMP Paul V. OQuinn, Jacksonville, Fla, assignor to J. C. Renfroe & Sons, Inc, Jacksonville, Fla., a corporation of Florida Filed Oct. 19, 1966, Ser. No. 587,711 14 Claims. (Cl. 294--104) ABSTRACT OF THE DISCLOSURE There is disclosed a lifting clamp having a movable gripping jaw, a shackle, a linkage connecting the shackle to the movable jaw and a locking mechanism engageable with the linkage to lock the jaw in either opened or closed positions, the locking mechanism having opposed latch members connected together by a separable connection.

This invention relates to clamps for lifting articles such as steel plates and more particularly to such clamps having a locking device to retain the clamp jaws in either an open or closed position.

The present invention is an improvement of the inventions disclosed in United States Patents 2,654,630, 3,297,354 and 3,370,881, all having a common assignee with the present invention.

Patent No. 2,654,630 discloses a clamp comprising a clamp body having a slot to receive an article to be lifted. A pair of jaws are provided on opposite sides of the slot. One of the jaws is movable between open and closed positions relative to the other jaw which is preferably fixed. The movable jaw is operated by a shackle connected to the movable jaw by force multiplying linkage.

The clamp body includes a pair of spaced side plates. Mounted on the inside of one of the side plates and parallel thereto is a pivotal locking plate operated by a handle lever located outside of such side plate. A heavy tension spring connects the locking plate to the linkage which extends between the shackle and the movable jaw. By rotation of the locking lever handle to a closed position the spring exerts a heavy closing force on the movable jaw. At the same time, however, the spring tends to cant the pivot pin connecting the locking plate to the handle to a position inclined relative to its normal axis. This causes a binding action which makes the lever difficult to operate.

Patent No. 3,297,354 discloses a clamp having a modified locking mechanism to eliminate the binding action mentioned above. The modified locking mechanism of this prior application gave rise to assembly problems. The present invention is directed to an improvement wherein the non-binding advantages of the clamp shown in this patent are achieved with a simpler, more easily assembled, more dependable structure.

An object of the present invention is to provide an improved lifting clamp of the general type disclosed in Renfroe Patent 2,654,630 having an easily operated locking mechanism free from binding and more particularly such a lock having a simple, rugged, durable construction and which is highly dependable, and may be easily assembled into the disassembled from the clamp body.

Another object is to provide such a locking mechanism having an easily assembled latch assembly having a handle means exterior of the clamp body, said handle means including a connecting bar rigidly mounted to the latch assembly or integral therewith.

Generally the invention relates to a lifting clamp which comprises a clamp body including a pair of spaced side members, said body defining a slot through said side Patented Dec. 3, 1968 members to receive an article to be lifted; a pair of opposed jaws mounted on opposite sides of said slot, at least one of said jaws being pivotally mounted for opening and closing movement relative to the other jaw; a shackle mounted for guided movement in said clamp body and adapted for connection to a lifting force; link means connecting said shackle to said movable jaw to close said movable jaw when a lifting force is applied to said shackle, said link means and said movable jaw forming an assembly; locking means comprising a pair of spaced latch'members rotatably connected to said side members of said body respectively for rotation about an axis, bipartite connecting means spaced eccentrically from said axis for securing said members together, said connecting means having first and second portions secured to said spaced members respectively and including cooperative means on said portions for transmitting a rotational force imposed upon one of said latch members to the other member, a spring means connecting said assembly to said connecting means, handle means operatively connected to at least one of said spaced members through an aperture defined in one of said side members for rotating said latch members to move said locking means between a closed position where said spring exerts a jaw closing force on said assembly and an open position where said spring permits said movable jaw to remain open, said connector means being spaced from said axis of rotation of said latch members a distance greater than the spacing between said axis of rotation and an edge portion of the side member of said clamp body opposite said side member having said handle means extending therethrough, whereby the latch member having a connecting bar of the handle means rigidly connected thereto or integrally formed therewith may be first pivotally connected to said side member by extending said bar through the aperture in said side member and then rotating said latch member to said edge portion to expose its portion of the connecting means whereby said latch members may be connected together by engagement of said connecting portions and the other latch member pivotally connected to the opposed side member of the clamp ibody.

Other advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein is set forth by way of example, a preferred embodiment of this invention.

FIGURE 1 is a front elevation of a lifting clamp em bodying the features of this invention;

FIGURE 2 is a right side elevation of the same clamp showing the locking assembly within the clamp body in a closed locked position;

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 2 showing the movable jaw in a closed position, its operating linkage and the lock mechanism assembly;

FIGURE 4 is a sectional view similar to FIGURE 3 showing the movable jaw in a locked open position;

FIGURE 5 is a left side elevation of the clamp in FIGURE 1;

FIGURE 6 is a sectional view taken along the line 6-6 of FIGURE 3 showing the fixed jaw of the clamping assembly and the shackle 'slidably mounted in a vertical slot in the clamp body;

FIGURE 7 is an exploded view of a portion of the locking mechanism, and

FIGURE 8 is a sectional view taken along the line 8-8 of FIGURE 1 showing the locking mechanism mounted between the spaced plates of the clamp body.

With reference to the drawings, the lifting clamp designated by the reference numeral 10 includes a clamp body 11 having a pair of spaced side members illustrated as plates 12 and 13. Preferably the side plates are permanently connected together by an elongated cross bar 14 to form a housing, and the lower end of bar 14 extends to a position close to but slightly spaced from the bottom edge of the side plates 12 and 13 as best shown in FIG- URE 3. The upper end of the cross bar 14 extends nearly to the top of the side plates 12 and 13. The cross bar 14 is permanently welded in place to provide a rigid and strong reinforcing for the clamp body. The termination of the bottom end of the cross bar 14 at a position slightly spaced from the lower edges of the side plates 12 and 13 facilitates the welding operation. With such spacing a fillet weld 15 may be placed along each corner of the bottom edge of the bar 14. If the bar 14 is flush with the bottom edge of the clamp body it would be necessary to bevel the ends of the bar to provide a weld along the corners of the bottom edge.

The side plates 12 and 13 are also connected together by a strut 16 which consists of a cylindrical sleeve 17 connected as a spacer between the side plates by a bolt 18, having a head 19 outside of the side plate 12.

The clamp body 11 defines a vertical slot 23 which extends through both of the side plates 12 and 13 to receive an article to be lifted. The clamp is particularly adapted for the lifting of heavy steel plates used in the construction industry, it being understood that many other different articles can be handled. The clamp body 11 partially houses a clamping assembly including a pair of jaws 24 and 25 mounted on opposed sides of the slot 23. The jaw 24 as illustrated is fixed against axial movement and the jaw 25 is movable as later described.

The jaw 24 is a conventional swivel jaw which is freely pivotable about its own axis around a connecting bolt 26 which is connected through an opening in the bar 14 and retains the jaw 24 against axial movement. The jaw 24 has a sharpened protruding ridge 27 (FIGURE 6) which grips the article being lifted.

Welded in face-to-face relation to the inner surface of the bar 14 is a face plate 28, having a circular opening 29 closely surrounding and corresponding to the circular periphery of the swivel jaw 24. As seen in FIGURE 6 the face plate 28 is T-shaped with a narrow upper portion 31 extending above the slot 23 between the side plates 12 and 13. Just above the top of the swivel jaw 27 the face plate 28 broadens out and extends to the extreme front and rear faces of the clamp body 11 to define a broad base portion 32.

The use of the separate face plate and backing bar 14 rather than a single bar eliminates the necessity for a counterbore in such bar to receive the swivel jaw 24. Time consuming machining operations are thus eliminated.

The movable jaw 25 is pivoted about a removable pin 35 which extends through the side plates 12 and 13. The jaw 25 has an arcuate serrated gripping face defining a plurality of sharpened teeth 26 which bite into the article being lifted.

Movable jaw 25 is also connected by a pin 37 to the lower end of an elongated link means 38, the upper end of which is connected by a pivot pin 39 to the lower end of a shackle 41. The link means 38 comprises a pair of opposed, spaced flat link bars 42 and 43 having the movable jaw 25 disposed therebetween.

The shackle pin 39 extends through both of the bars 42 and 43 and into a pair of opposed vertical slots 44 and 45 in the interior surface of the side plates 12 and 13. The shackle 41 is movable vertically in the clamp body by the sliding action of the pin 39 in the slots 44 and 45. The slots limit the non-rotational movement of the pin 39 to a vertical path. The shackle at its upper end has a lifting connection formed by a large opening 46 adapted to receive a conventional lifting hook at the end of a hoisting cable.

When the clamp 10 is mounted on a plate which is in a horizontal position with the movable jaw on top of the plate, application of lifting force to the shackle 41 causes said shackle 41 to pivot and engage the sleeve 17 which serves as a fulcrum thereby causing the shackle to raise the pin 39 in the slots 44 and and applying a closing force to the jaw 25 in the manner fully described in Patent 2,654,630. When a force is applied to the shackle 41 in a horizontal (relative to the vertical slot 23) direction toward the swivel jaw 24, the shackle engages the top of the bar 14 which serves as a fulcrum causing the pin 39 to be raised and the jaw 25 to be closed.

Thus the elongated bar 14 functions both to reinforce the clamp body and to serve as a fulcrum for the shackle 41. The upward extension of the bar 14 above the uppermost position of the movement of the shackle pin 39 reinforces the clamp body 11 and minimizes the chance of failure of the side plates 12 and 13 along a line extending diagonally upward and across the bar 14 from the top of the slot 23. This construction enables the lateral width of the clamp body 11 on the swivel jaw side of the slot 23 to be substantially less than in prior art clamps. The present clamp 10 thus can be used in places Which would be inaccessible to prior art clamps.

As shown in FIGURES 3 and 4, the shackle 41 may be moved between an elevated position as shown in FIGURE 3, and a depressed position as shown in FIGURE 4, in which the movable jaw 25 is closed and opened re spectively. As also shown in these figures the lower corner 51 of each of the side plates 12 and 13 covers the assembly composed of movable jaw 25 and the link means 38 during the entire path of movement of such assembly except that the gripping portion of the movable jaw is exposed in the slot 23.

An important feature of the present invention is in its improved locking mechanism or assembly 52 which is broadly comprised of a latch assembly 53 and a spring means 54 connected at one end thereof to said latch assembly 53 and connected at the other end thereof to said link means 38 for locking said link means 38 in a position wherein said movable jaw 25 is spring biased into engaging relation with the article to be lifted. The spring means 54, as illustrated, is a heavy tension spring having an end portion connected to said latch assembly 53 with its opposed end portion operatively connected to the link bars 42 and 43 at a point eccentric with the pin 37 which serves to pivotally connect the movable jaw 25 to the bars 42 and 43, whereby the spring 54 when positioned by the latch assembly 53 imposes a force on the bars 42 and 43 holding the movable jaw 25 in engaging relation with the article to be lifted.

The latch assembly 53 includes a pair of spaced latch members illustrated as a latch cam 55 and a latch pawl 56. The cam 55 and pawl 56 are coupled together by a connector means 57 whereby a rotational force imposed on a latch pawl 56 is transmitted to the latch cam 55 by the engagement of abutting surfaces in the separable connector 57. The latch pawl 56 and latch cam 55 are each pivotally connected to the side members 12 and 13 of the clamp body 11 for rotation about an axis substantially transverse to the plane of the side members 12 and 13. The rotation of the latch pawl 56 and latch cam 55 effects an eccentric rotation of the connector 57 about said axis of rotation thereby displacing an end portion of the tension spring 54 carried by connector 57 causing said spring 54 to impose a locking force on the link bars 42 and 43 of the link means 38.

The latch pawl is non-rotatably connected to a latch handle 58 by means of a connecting bar 59 which is rigidly connected or may even be integrally formed with said latch pawl 56 with the latch handle 58 secured to the connecting bar 59 exteriorly of the side member 13 by means of a tension pin 60. Due to the torque imposed by operation of the handle 58 in opposition to the force of the spring 54, the bar 59 should be rigidly mounted to the latch pawl 56 to provide a durable latch assembly. The latch cam 55 is pivotally mounted to the side member 12 by means of a cap screw and nut assembly 61 received through an aperture 62 defined in the side member 12 with the head of the cap screw received through a bore 63 defined in the latch cam 55. The employment of a pair of opposed pivot points for rotatably connecting the latch assembly 53 within the space defined between the pair of spaced members 12 and 13, allows the latch assembly 53 to be freely rotated about said axis avoiding a binding action encountered in latch assemblies employing a single pivot point caused by the cantilevered force loading of the spring member thereon.

The separable connector 57 coupling the latch pawl 56 to the latch cam 55 includes separate portions carried by the latch pawl 56 and latch cam 55 respectively and engageable upon rotation of the latch handle 58 and latch pawl 56 to impart a rotational driving force to the latch cam 55 such that the entire locking latch assembly 53 rotates about a desired axis defined through the pivot points of connection of the spaced latch pawl 56 and latch cam 55 to the side members 12 and 13. In the illustrated embodiment, the separable connector 57 is comprised of a sleeve member 64 carried by the latch pawl 56 and a pin or bar member 65 suitably carried by the latch cam 55 and receivable in the interior bore 66 of the sleeve member 64 such that the side walls of the sleeve member 64 form an abutment surface with the pin 65 for imparting the rotational driving force imposed on the handle 58 to the latch cam 55. The pin 65 and bore 66 are generally coextensive with the spacing between said latch members 55 and 56 to provide a maximum bearing surface.

A primary advantage of the novel structure of the locking assembly 52 is in its double pivot connection to the clamp body 11, coupled with the facility with which the latch assembly 53 may be assembled in the clamp body 11 between the spaced side members 12 and 13 even with the inclusion of a connecting bar 59 rigidly mounted to the latch pawl 56 or integral therewith. The latch pawl 56 may be inserted between the interior faces of the side members 12 and 13 of the clamp body 11 extending the rigidly mounted connecting bar 59 through an aperture 67 defined in the side member 13 and connecting the bar 59 to the latch handle 58 by means of a tension pin 60, said handle 58 being disposed exteriorly of the clamp body 11. The connector 57 is disposed on the latch members 55 and 56 at a spacing from the axis of rotation of said members 55 and 56 greater than the spacing between said axis of rotation and an edge portion 68 of the side member 12 whereby the latch pawl 56 may then be rotated to a position where the sleeve member 64 clears, is exterior of or is exposed about said edge portion 68 of the side member 12 such that the pin 65 may be inserted into the bore 66 of the sleeve member 64 placing the latch cam 55 in cooperative relation with the latch pawl 56. The edge portion 68 may be an end edge of a side member as illustrated, or may simply define an opening through said member sufiiciently large for passage therethrough of the latch member 55. The screw 69 may then be extended through the aperture or 'bore 63 defined in the latch cam 55 and through the aligned aperture 62 in the side member 12 and retained therein by means of a nut 70 thereby forming an inwardly extending lug comprised of the head 71 of the screw 69 about which the latch cam 55 may rotate in response to a rotation of the latch handle 58.

The tension spring member 54 having a hooked end portion 72 may then be connected to the latch assembly 53 by placing said hook 72 over the connector means 57 about the sleeve member 64. It is readily apparent that a rotation of the latch assembly 53 about an axis moves the connector 57 eccentrically about the said axis in such a manner that the coil tension spring 54 is placed in a tensioned state exerting a force on the link means 38 thereby retaining said linkage in such a position to hold the movable jaw 25 in an engaging relation to the article being lifted whereby a relaxation of the lifting force on the shackle 41 will not effect an opening of the movable jaw 25 causing a release of the article retained between the jaws 24 and 25.

The cam latch 55 defines a cam or abutment surface 73 engageable with a mating surface 74 defined on the bar 42 of the link means 38 to retain the link means 38 in a position wherein the movable jaw 25 is open, as illustrated in FIGURE 4 thereby leaving the slot 23 defined in the clamp body 11 free of obstruction from the forward serrated face of the movable jaw 25. The latch cam thereby effects a retaining force on the link means 38 preventing the activation of said link means 38 when a lifting force is applied to the shackle 41. In this manner, when the lifting clamp 10 is received at a position for engaging a particular article, the slot 23 is open as is the jaw 25 to receive said article with the jaw 25 being moved or rotated into position in an engaging or clamping relation with said article by a rotation of the latch handle 58 to swing the cam surface 73 out of retaining relation of surface 74 on the link bar 42 allowing a lifting force on the shackle 41 to lift said bar 42 causing the movable jaw 25 to rotate about pin 35 into engaging relation with the article to be lifted.

Manual rotation of the handle 58 causes rotation of the locking latch members 55 and 56 about the axis of the pivots 59 and 61, the connector 57 being eccentric with said axis. When the handle 58 is rotated to a closed position as shown in phantom lines in FIGURE 3 the locking latch members 55 and 56 assume the position shown. The locking assembly 52 is held in locked position by an overcenter mechanism with the tension spring 54 exerting a closing force on the assembly of the link means 38 and the movable jaw 25. In this position the axis of the spring 54 is inside of the axis of rotation of the latch members. Further rotation of the locking plate members is preventer by engagement of the handle 58 with the head 19 of the bolt 18. Moreover, a protruding pawl 82 on the latch pawl 56 engages the sleeve 17 which also functions as a stop member.

When the handle 58 is rotated in a clockwise direction as shown in FIGURES l and 3 and until the axis of the spring 54 passes to the outside of the axis of rotation of the latch members 55 and 56, the spring 54 then pulls the handle 58 down toward the open position shown in phantom lines in FIGURE 4. In that position the spring 54 exerts no closing force on the movable jaw 25 which is permitted to remain fully open.

The general operation of the clamp is the same as that more fully described in Patent 2,654,630.

There has been illustrated and described what is considered to be a preferred embodiment of the invention. It will be understood, however, that various modifications may be made by persons skilled in the art without departing from the scope of the invention which is defined solely by the appended claims.

What is claimed is:

1. A locking assembly for use in a lifting clamp of the type which includes a body having a pair of spaced side members housing therebetween a clamping assembly including a pair of opposed clamping jaws, at least one of said jaws being movable, and a linkage means operatively connected to said movable jaw and responsive to a lifting force for opening and closing said movable jaw relative to the other jaw for clamping engagement of an article to an article to be lifted therebetween, said locking assembly comprising:

a latch assembly including a pair of spaced latch members rotatably connected to said side members respectively for rotation about an axis and connecting means including separate portions secured to said latch members respectively, said portions being mutually engageable for transmitting a rotational force imposed on one of said latch members to the other of said latch members;

spring means operatively connected at one end thereof to said latch members eccentrically of said axis and at the other end thereof to said linkage means for locking said linkage means with said jaw in an article engaging position, whereby the force of said spring is imposed on both of said latch members; and

means operatively connected to at least one of said latch members for rotating said latch members about said axis to move said connecting means between a first position where said spring exerts a jaw closing force on said linkage means and a second position Where said jaw closing force of said spring on said linkage means is relieved.

2. A locking assembly, as recited in claim 1, wherein said connecting means in said latch assembly is eccentrically spaced from said axis and wherein said one end of said spring means is connected to said connecting means.

3. A locking assembly, as recited in claim 1, wherein said means for rotating said latch members includes a bar member rigidly mounted to one of said latch members and wherein one of said side members of said clamp body defines an aperture therethrough, said bar member being received through said aperture and being rotatable insaid aperture to rotate said latch assembly about said axis.

4. A locking assembly, as recited in claim 3, wherein said bar member is integral with said latch member.

5. A locking assembly as recited in claim 3 wherein one of said portions of said connecting means includes means defining a receiving opening therein and wherein said other portion includes a means receivable in said opening for transmitting a rotation force applied to one of said latch members to the other of said latch members.

6. A locking assembly as recited in claim 5 wherein the spacing between said connecting means and said rotational axis of said latch members is greater than the spacing between said axis of rotation and an edge portion of the side member of said clamp body opposite said side member having said bar member extending therethrough, whereby the latch member having said bar mounted thereto may be first pivotally connected to said side member by extending said bar through said aperture and then rotating the latch member to said edge portion to expose its portion of the connecting means whereby said latch members may be connected together by engagement of said connecting portions of the connecting means and the other latch member pivotally connected to the opposed side member of said clamp body.

7. A locking assembly as recited in claim 6 wherein said opening defining means includes a sleeve member defining a bore to receive the force transmitting means of said other portion.

8. A locking assembly as recited in claim 7 wherein said force transmitting means is comprised of a pin member receivable in a telescoping manner in said bore of said sleeve member and wherein said pin and said sleeve member are generally coextensive with the spacing between said latch members.

9. A lifting clamp comprising:

a clamp body including a pair of spaced side members;

a pair of opposed jaws operatively connected to said clamp body, at least one of said jaws being movable for opening and closing movement relative to said other jaw to clampingly engage an article therebetween;

linkage means operatively connected to said movable jaw and responsive to a lifting force for opening and closing said movable jaw relative to said other jaw; and

locking means operatively connected to said linkage means for locking said movable jaw in a closed, article engaging position, said locking means including a pair of spaced latch members, each pivotally connected to an opposed side member respectively, handle means extending through an aperture defined in one of said side members and secured to one of said latch members for rotating said latch members about an axis and means operatively connected to each of said latch members for transmitting said rotational force applied to said latch member having said handle connected thereto to the other of said latch members, said connector means having separate portions connected to said latch members respectively, said portions being mutually engageable for transmitting said rotational force between said latch members.

10. A lifting clamp as recited in claim 9 wherein said connecting means between said spaced latch members is eccentrically located relative to said axis of rotation of said latch members and wherein said locking means includes a spring means operatively connected at one end thereof to said connecting means and operatively connected at the other end thereof to said linkage means for imposing a spring bias on said linkage means when said latch means is rotated to a predetermined position for locking said jaw in an article engaging position wherein the release of the lifting force on the linkage means will not effect an opening of said movable jaw.

11. A lifting clamp as recited in claim 10 wherein said handle means includes a connecting bar member integral with said latch member and extended through said aperture in said side member.

12. A lifting clamp as recited in claim 10 wherein one of said portions of said connecting means includes means defining an opening therein and wherein the other of said portions includes means receivable in said opening for transmitting said rotational force whereby rotation of one of said latch members causes rotation of the other of said latch members.

13. A lifting clamp as recited in claim 12 wherein the spacing between the connecting means and the rotational axis of said spaced latch members is greater than the spacing between said rotational axis and an edge portion of the side member opposite said side member of said lifting clamp body having said handle means extending therethrough whereby the latch member having said handle means connected thereto may be first pivotally connected to said side member by extending said handle means through said aperture and then rotating its portion of said connecting means to said edge portion whereby said latch members may be connected together by engagement of said connecting portions and the other latch member pivotally connected to the opposed side member of said clamp body.

14. A lifting clamp as recited in claim 13 wherein said opening defining means on one of said portions of said connecting means includes a sleeve member defining a bore to receive the force transmitting means of the other portion.

References Cited UNITED STATES PATENTS 2,446,610 8/1948 Renfroe 294104 2,654,630 10/1953 Renfroe 294104 3,178,219 4/1965 Renfroe 294-104 3,297,354 1/1967 Renfroe 294-104 ANDRES H. NIELSEN, Primary Examitlf. 

